2. analog
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Went from brilliant to distortion

I'm wishing for a spare phono preamp. 

I recently purchased a Rega P10. My wife and I have been amazed at the amount of information this table draws out of our old vinyl collection. On well recorded vinyl it's jaw dropping. I couldn't be more pleased witrh the P10's performance.

Now all of a sudden my music is distorted. Distortion in the form of noise surrounding the music. It's bad. Unlistenable. 
I had a made a change in that my Rogue Audio Ares formally fed my Lindemann Musicbook DSD used as a preamp to feed my amplifers and it all worked brilliantly. A few days ago I built a system in our den stealing the Lindemann and using our NAD M17/V2 as a preamp instead. That's when music went south. I thought that odd as the NAD is performing well in its own domain, as a digital streamer and SSP. 

I checked the tubes on the Ares but noted that both channels are distorted. Can't have 2 tube failures identically in left right channels right? OK, maybe the analog input on the NAD went south so I moved to another analog in to no help. Well, it was working perfectly through the Lindemann so I carried my vinyl setup to the den and reconnected to the Lindemann. Same distortion. 

Unless I'm missing something this leaves a problem with the Rogue Ares not related to a tube or a problem with the Apheta 3 cartridge which is nearly new. 

Anyone have an insight?
Thanks
128x128desalvo55
desalvo55's avatar
desalvo55 OP
257 posts
 
Yes,  had everything back to original.

I located a pair of JJ ECC802-S tubes and replaced the 12AX7LPS Sovteks out of the rearward position of the L/R channels of the Ares. 

No more noise! No electronics expert here but I know (or I think I know) that 1 tube failure can effect both channels - it seems.

As I recall, the JJ's needed a lot of gain to get the system going.

Thanks guys for you help!
noromance's avatar
noromance
9,766 posts
 
Interesting. The moving upset things somehow. The 2 triode amplifying elements in each tube can be allocated to a channel each. The 802s are a different tube with lower gain but higher current. 
limomangus's avatar
limomangus
1,426 posts
 
MAN that's a shame that Rega P10 and your equipment are Outstanding. 
lewm
13,001 posts
 
desalvo, Do I understand correctly that you replaced 12AX7s with ECC802?  The ECC802 is equivalent to a 12AU7, which is a much different tube electrically, compared to a 12AX7, as noromance already suggested.  You made some remark about needing more gain, and I am not surprised; the 12AU7 is much lower in gain than the 12AX7 and would not suffice as the gain tube in most phono stages.  The right thing to do is to replace 12AX7s with 12AX7s or ECC83s or ECC803s.  However, you mention that the tubes were in the "rear" position on the Ares.  Does that mean they are near to the output jacks?  If so, the circuit may use 12AX7 as a cathode follower.  (A tube that converts voltage to current and reduces output impedance, essentially.) 12AX7s are not a really good choice for cathode follower; 12AU7/ECC82/ECC802 is a better choice, but to make full use of the latter tube, you would need to change some resistors in that stage.  So, it's still best to stick with 12AX7 or its congeners.
desalvo55's avatar
desalvo55 OP
257 posts
 
I am forever a student of audio. At this "hobby" for 54 years, so I'm in second grade. I might actually be unlearning crap at this point. I read posts from many of you that speak of cartridge loading, VTA, on and on and I'm like "hope I got good tubes". Well at least I can laugh at myself.

I still have my first turntable, a Technics direct drive SL1700. I bought a VPI Scoutmaster many years back and it's for sale to make room for the Rega. But I honestly don't know nearly as much with analog as I do with digital. I have built a very ah, robust digital system paying attention to every bit (bit) of technology and subtleties. My digital rig sounds very well. The Rega beats it hands down. I'm in awe of what the Rega can pull out of vinyl and pull it in its analog way. Seriously, the Rega might be the best piece of audio equipment I've ever bought, and I have gone through a lot of gear!

I might have a small black cloud over my stereo's. I just built a pair of monitors which played very well. I pulled the drivers to perform finish work on the cabinets. When I reassembled the drivers, one woofer didn't woof. It measured open on my fluke. It was a kit and I'm hopeful it will get replaced. It's been frustrating but hey, I'm spoiled.

Still pondering a phonostage that compliments well with the P10.
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